I want to chime in and say that we’re having the same issue. Got a call from a client who told me that every time he loaded a page on his site, it came up blank. It wasn’t happening to me but I was logged in to WP with the caching option off for logged in users.
I was able to duplicate the problem and was getting blank pages. I turned off WP Super Cache and everything works fine.
And finally, I had only updated to WP 4.2.1 a day ago or so. So it looks as if the issue is a conflict between WP 4.2.1 and WP Super Cache.
Just my two cents.